and its application to Fire Alarms. 65 
observed that either or both of the wires may be broken in a 
single place, and yet every Signal Station will be in communica- 
in one or the other di- 
rection. By this ar- 
rangement, therefore, 
the principle of double 
conductors is preserv- 
s an additional 
Safeguard, the inter- 
ruption of either of the 
wires in a single place 
would be known at 
the Signal Stations themselves where the wires approach, there 
is the possibility of a cross connection, if the open circuit 1s 
used, 
Stations like the links of a chain, as in fig. 3. Owing to the dif- 
culty of keeping the wires sufficiently separated in all parts of 
the System in Boston, and the occasional use of posts, as in cross- 
ing the South Boston bridge, the 
Closed circuit will be partially if 
Not altogether used with the Sig- 
nal wires. | 
The Alarm Circuit is so arrang- 
ed that it may be completed by 
depressing a key at the Central 
ce. In fig. 3, B represents the 
battery at the Central Office, and 
the Alarm Key. S, 8, S, are 
Stations, such as churches, 
where the machinery is placed by 
bs ich the bell is struck when < : tien : 
vitcuit is completed. Several o ME. Oe ee 
these may be included in the same Cireuit. _ The double Vom 
Skoonp Szezs, Vol. XII, No. 37.—Jan, 1852. Gf a akon 
